Tyrian purple was one of the costliest and most mysterious of the dyes of ancient times. Used first by the Phoenicians, it was taken from the secretions of several species of mollusks, Murex brandaris and Purpura haemostoma and was reserved for use by royalty, priests and nobles. In Rome the Caesars declared it their official color and claimed exclusive rights to its production.
Dyeing with Murex and Purpura is a complex process which involves extracting the liquid while the mollusk is still alive and exposing it to sunlight for a specified period of time, during which the dye changes color. It can take up to 12,000 mollusks to produce 1 gram of dye.
With the fall of the Roman and after it the Byzantine Empire, the European understanding of purple dyeing fell away and by the 14th century the secrets of Tyrian purple were lost. It has only been through recent experimentation that the technique was rediscovered in 2001.